U.S. patent number 10,598,718 [Application Number 15/248,598] was granted by the patent office on 2020-03-24 for method and device for insulation fault location having an adaptive test current determination.
This patent grant is currently assigned to BENDER GMBH & CO. KG. The grantee listed for this patent is Bender GmbH & Co. KG. Invention is credited to Dieter Hackl, Oliver Schaefer.
United States Patent |
10,598,718 |
Hackl , et al. |
March 24, 2020 |
Method and device for insulation fault location having an adaptive
test current determination
Abstract
The invention relates to a method for insulation fault location
in an IT power supply system, comprising the process steps: feeding
of a test current, detecting of a test current portion in a branch
of the IT power supply system and evaluating the detected test
current portion. Furthermore, the invention relates to an
insulation fault location for an IT power supply system having a
test current generator for supplying a test current, having a test
current sensor for detecting a test current portion in a branch of
an IT power supply system and having an analyzing device for
evaluating the detected test current portion. According to the
invention, the insulation fault location system comprises a
computing unit for adaptively determining a test current parameter
of the test current depending on an electric system parameter of
the IT power supply system.
Inventors: |
Hackl; Dieter (Fernwald,
DE), Schaefer; Oliver (Gruenberg, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bender GmbH & Co. KG |
Gruenberg |
N/A |
DE |
|
|
Assignee: |
BENDER GMBH & CO. KG
(Gruenberg, DE)
|
Family
ID: |
57153244 |
Appl.
No.: |
15/248,598 |
Filed: |
August 26, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170067953 A1 |
Mar 9, 2017 |
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Foreign Application Priority Data
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Sep 3, 2015 [DE] |
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10 2015 216 915 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R
31/52 (20200101); G01R 31/14 (20130101); G01R
31/088 (20130101); G01R 31/50 (20200101); G01R
27/18 (20130101) |
Current International
Class: |
G01R
31/08 (20200101); G01R 27/18 (20060101); G01R
31/14 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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104714124 |
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Jun 2015 |
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CN |
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104793054 |
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Jul 2015 |
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CN |
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102011050590 |
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Nov 2012 |
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DE |
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102013218836 |
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Mar 2015 |
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DE |
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1593983 |
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Nov 2005 |
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EP |
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1855366 |
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Nov 2007 |
|
EP |
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2664932 |
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Nov 2013 |
|
EP |
|
2851692 |
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Mar 2015 |
|
EP |
|
Primary Examiner: Reisner; Noam
Attorney, Agent or Firm: King & Schickli, PLLC
Claims
The invention claimed is:
1. Method for insulation fault location in an IT power supply
system (4), comprising the process steps: supplying of a
pulse-shaped test current (IL), detecting of a test current portion
in a branch of the IT power supply system (4), evaluating the
detected test current portion, characterized by adaptive
determining of a test current parameter of the test current (IL)
depending on an electric system parameter (24, 26) of the IT power
supply system (4), wherein as the electric system parameter of the
IT power supply system (4), an insulation resistance is
evaluated.
2. Method according to claim 1, characterized in that a test
current amplitude is adaptively determined as a test current
parameter.
3. Method according to claim 1, characterized in that a test
current pulse duration of the pulse-shaped test current (IL) is
adaptively determined as a test current parameter.
4. Method according to claim 1, characterized in that a specific
supply of a test current (IL) in a conductor phase (L1, L2, L3) of
the IT power supply system (4) is carried out.
5. Method according to claim 1, characterized in that one or more
of the following parameters of the IT power supply system (4) are
evaluated as electric system parameters (24, 26): distribution of
the insulation resistance on individual conductor phases, network
leakage capacitance, momentary displacement voltage, maximum
admissible displacement voltage, maximum admissible active power in
a fault resistance, time limitation for the flow of a maximum test
current.
6. Method according to claim 1, characterized in that one or more
of the following system-related specifications are evaluated as
electric system parameters (24, 26): system-relevant standards,
specifications of the system configuration, safety-critical
categorization.
7. Method according to claim 1, characterized in that the electric
system parameter (24, 26) is statically configured or dynamically
determined.
8. Method according to claim 1, characterized in that a sequence of
the adaptive determination of the test current parameter is set by
means of a computer program (20).
9. Method according to claim 8, characterized in that the computer
program (20) accesses an expert knowledge base (22) and adaptively
adjusts the test current parameter or proposes the determined test
current parameter for use, taking into account the electric system
parameter (24, 26).
10. Insulation fault location system for an IT power supply system
(4) having a test current generator (8) for supplying pulse-shaped
a test current (IL), having a test current sensor (10a, 10b) for
detecting a test current portion in a branch of an IT power supply
system (4), having an analyzing device (12) for evaluating the
detected test current portion, characterized by a computing unit
(14) for adaptively determining a test current parameter depending
on an electric system parameter (24, 26) of the IT power supply
system (4), wherein as the electric system parameter of the IT
power supply system (4), an insulation resistance is evaluated.
Description
This application claims the benefit of German Patent Application
Ser. No. 10 2015 216 915.4, filed Sep. 3, 2015, the disclosure of
which is incorporated herein by reference.
TECHNICAL FIELD
The invention relates to a method for insulation fault location in
an IT power supply system, comprising the process steps: feeding of
a test current, detecting of a test current portion in a branch of
the IT power supply system and evaluating the detected test current
portion.
Furthermore, the invention relates to an insulation fault location
system for an IT power supply system, having a test current
generator for supplying a test current, having a test current
sensor for detecting a test current portion in a branch of an IT
power supply system and having an analyzing device for evaluating
the detected test current portion.
BACKGROUND
Due to the inherent safety of IT power supply systems (French:
Isole Terre--IT), a continuous power supply of the user supplied by
the IT power supply system can be ensured, even if a first
insulation fault has occurred, since the active parts of the IT
power supply system are separated from the ground potential--with
respect to "ground"--and a closed electric circuit cannot be formed
in this first fault case. A first insulation fault occurs, for
example, if there is an unintended electric connection between an
active conductor of the IT power supply system and the conductive
casing of an operating part (user).
Provided that the insulation state of the IT power supply system is
continuously monitored by an insulation monitoring device, the IT
power supply system can still be operated without a time
limitation, even when a first fault has occurred, however, the
first fault is to be removed as quickly as practically possible
according to the recommendation of standards DIN VDE 0100-410 and
IEC 60364-4-41, respectively.
A first insulation fault is recognized and reported by the
insulation monitoring device. This report starts an insulation
fault location by a test current being produced by a test current
generator of an insulation fault location system and being supplied
into the IT power supply system at a central location. In the
branches of the IT power supply system involved in the fault
location, a test current sensor detects whether a significant test
current portion flows into the respective branch.
The signals of the test current sensor are centrally detected in an
analyzing device and an insulation fault localization is carried
out based on these signals.
According to the state of the art, the test current parameters, in
particular the test current amplitude as well as the test current
pulse duration with a pulse-shaped test current, of the test
current produced and supplied by the insulation fault location
system are set once when planning and installing the
safety-critical measures for the IT power supply system. Thereby, a
compromise is to be made between the following requirements: (1)
preventing risk to persons and preventing fire hazards by the test
current, (2) no impediment of the function of the IT power supply
system and the connected operating parts by the test current and
(3) localization of even high-resistance insulation faults.
In practice, the test current is limited to a few 10 mA or even
only a few mA in order to safely fulfill the requirements (1) and
(2).
In particular in widely branched IT power supply systems, problems
regarding the size and/or the distribution of network leakage
capacitances can occur. These network leakage capacitances are
mostly electrically parallel to the fault resistances to be
detected. A portion of the test current therefore flows through
these capacitances and, when the test current is set too low, leads
to high-resistance fault resistances not being detected, in a worst
case scenario. The distribution of the test current on multiple
faulty branches in a badly maintained IT power supply system poses
another problem. Multiple faults are difficult to detect with small
test current amplitudes, since the low test current distributes
itself on multiple fault resistances and the sensitivity threshold
of the test current sensors can fall short. Ultimately, disturbing
elements can occur in IT power supply systems which impede or
prevent an insulation fault location, should the test current
portion in the faulty branch is so low that it is hidden by
disturbing signals and cannot be detected or detected sufficiently
exact by the test current sensor.
The circumstances mentioned above can therefore result in an
insulation fault not being located.
Known measures for solving these problems consist of a manual
adjustment of the test current parameter, on the one hand, for
example by manually increasing the test current amplitude, as far
as this is possible in the installed insulation fault location
system. However, since the estimation of a maximal admissible test
current amplitude requires considerable expertise in a present
fault case, service personnel trained specifically in this area is
employed for this purpose. Thus, the maintenance measures are
delayed and increase in price in an unfavorable way.
As an additional measure, on the other hand, the insulation fault
location system or components of the installed insulation fault
location system can be substituted by a system having a higher test
current amplitude, provided such a system is available on the
market. A substitution of such components in critical IT power
supply systems often requires a renewed inspection by an
expert.
Furthermore, the fact that the test current amplitude of currently
available insulation fault location systems is limited to low
values of only a few 10 mA by the producer is still another
disadvantage. Therefore, the only possibility that remains in the
problematic cases mentioned above is to carry out the fault
location without the help of insulation fault location systems, for
example by shutting down branches (sub-systems).
The solutions mentioned above are therefore not always satisfactory
in practice. Moreover, a delay in localizing and removing a first
fault can lead to an unnecessary strain on the IT power supply
system or even to a shutting down of the power supply.
Therefore, the object of the present invention is to enhance a
method and a device for insulation fault location in such a way
that a reliable insulation fault location can be carried out in an
economically feasible way, wherein at the same time a high electric
safety is ensured.
SUMMARY
With respect to a method, this object is attained in connection
with the preamble of claim 1 in that a test current parameter of
the test current is adaptively determined depending on an electric
system parameter of the IT power supply system.
The idea of the present invention is based on automatically
adjusting at least one characterizing parameter of the test
current, in particular the current amplitude and the current
(signal) form, to the IT power supply system in such a way that an
adequate test current for the optimal fault location, according to
the requirements (1) to (3) mentioned above, is supplied. The test
current is automatically adjusted to the configuration and the
electric state of the IT power supply system on request or in set
updating intervals depending on, meaning considering and
evaluating, at least one electric system parameter of the IT power
supply system.
In another embodiment of the invention, a test current amplitude is
adaptively determined as a test current parameter.
A parameter for describing the test current is its amplitude (test
current amplitude). This test current amplitude is automatically
determined according to a predetermined computing instruction
depending on an electric system parameter of the IT power supply
system, preferably depending on the size of the insulation
resistance.
Thus it is obtained that an optimal maximum test current required
for fault location can be used without causing a risk to persons or
device components.
Furthermore, a test current pulse duration of a pulse-shaped test
current is adaptively determined as a test current parameter.
Another parameter for describing the test current presents the test
current pulse duration in a pulse-shaped test current. Depending on
at least one electric system parameter of the IT power supply
system, the test current pulse duration is adaptively
determined--preferably depending on the size and distribution of
the network leakage capacitances in order to enable their complete
charging and to be able to carry out the measurement in a steady
state.
Hence, a temporally optimized determination of the fault position
results in connection with the possibility to also be able to
recognize high-resistance insulation faults.
A specific supply of a test current into a conductor phase is
carried out advantageously.
The specific supply of the test current into a conductor phase
enables the use of a maximum test current without the function of
the IT power supply system being negatively influenced. Thereby,
the specific supply can also consist in a weighted distribution of
the (entire) test current, wherein the test current is adaptively
determined for every conductor phase of the IT power supply system
in such a way that a maximum test current regarding its amplitude
is supplied with an optimally adjusted test current pulse duration
without causing a risk to persons or an impediment of a
function.
One or more of the following parameters of the IT power supply
system are evaluated as electric system parameters: insulation
resistance, distribution of the insulation resistance on individual
conductor phases, network leakage capacitance, momentary
displacement voltage, maximum admissible displacement voltage,
maximum admissible active power in a fault resistance, time
limitation for the flow of a maximum test current.
One or more of the following system-related specifications are
evaluated as another electric system parameter: system-relevant
standards, specifications of the system configuration,
safety-critical categorization.
In a preferred embodiment of the invention, the electric system
parameter is statically configured or dynamically determined.
As a statically configured electric system parameter, the parameter
or the indication to be evaluated is saved as a set value in a
storage device. The dynamic determination of the electric system
parameter can be carried out by direct measuring or by data
transfer of an already determined parameter, for example by
communication of the insulation resistance via a data connection
coming from an insulation monitoring device.
It is advantageous if a sequence of the adaptive determination of
the test current parameter is set by means of a computer
program.
The adaptive determination of the test current parameter is carried
out by software controls via program commands. This opens up the
possibility of flexibly reacting to changes to the IT power supply
system or to changed requirements.
A possible approach to adjust the optimal test current amplitude
required for fault location, for example, is to slowly increase the
test current amplitude until an analyzing device detects a faulty
branch or the maximum admissible test current amplitude has been
reached or a different relevant electric system parameter of the IT
power supply system has been reached, which prohibits any further
increase of the test current amplitude.
The computer program accesses an expert knowledge base and
adaptively adjusts the test current parameter or proposes the
determined test current parameter for use, taking into account the
electric system parameter.
Retrievable expert knowledge on an optimal approach for the
insulation fault location is saved in the insulation fault location
system, said approach using the known relevant electric system
parameters of the IT power supply system in order to adjust the
optimal test current parameter required for fault location or to
propose the determined parameter value to the user of the
application.
With respect to a device, the object of the invention is attained
in connection with the preamble of claim 10 by the insulation fault
location system comprising a computing unit for adaptively
determining a test current parameter depending on an electric
system parameter of the IT power supply system.
When realizing the method according to the invention, the
insulation fault location system comprises a computing unit
according to the invention which comprises a software technical
implementation of the adaptive parameter determination.
The insulation fault location system according to the invention and
the method based on the insulation fault location system enable to
supply an adaptively determined test current optimally suitable for
fault location without further expertise of the service
personnel.
The attained simplification in the execution of the insulation
fault location leads to an increased safety during operation and
maintenance of an IT power supply system, since the fault
localization is carried out faster, thus preventing risks which
occur due to an insulation fault. Thereby, the insulation fault
location is made significantly more reliable and economical, in
particular in complex IT power supply systems.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
Other advantageous embodiment features become apparent from the
following description and from the drawing, which illustrates a
preferred embodiment of the invention with the aid of an example.
In the drawing:
FIG. 1 shows an insulation fault location system according to the
invention and
FIG. 2 shows schematically the principle of the adaptive
determination of a test current parameter according to the
inventive method.
DETAILED DESCRIPTION
FIG. 1 shows an insulation fault location system 2 according to the
invention in a three-phase IT power supply system 4 having two
branches which each supply a user 6a, 6b. The IT power supply
system 4 is further characterized by the leakage capacitances Ce1,
Ce2 and the insulation resistances Riso1, Riso2.
The IT power supply system 4 is monitored by an insulation
monitoring device 3 which imprints a measuring current Im into the
IT power supply system 4 for defining the entire insulation
resistance of the IT power supply system 4.
The insulation fault location system 2 comprises a test current
generator 8 which imprints a test current IL, independent from the
measuring current Im of the insulation monitoring device 3, between
the live conductors L1, L2, L3 and the ground PE into the IT power
supply system 4. A test current sensor 10a, 10b is arranged in each
of the branches of the IT power supply system, said sensor 10a, 10b
detecting a test current portion flowing in the branch. If there is
an insulation fault Rf at the user 6a, as illustrated in FIG. 1,
the test current portion detected by the test current sensor 10a is
non-zero in this faulty branch and the test current sensor 10a
sends a respective measuring signal to an analysis device 12. The
analysis device 12 receives the measuring signals of all test
current sensors 10a, 10b and localizes the fault position based on
the allocation of test current sensor/branch.
According to the invention, the insulation fault location system 2
comprises a computing unit 14 which adaptively determines the test
current IL, in particular its characteristic parameters test
current amplitude and test current pulse duration.
The principle of the adaptive determination of a test current
parameter of the test current IL according to the inventive method
is illustrated in FIG. 2. A computer program 20 forms a central
element, said computer program 20 carrying out the adaptive
determination by means of program commands. Thereby, the computer
program 20 accesses an expert knowledge base 22 which comprises
instructions regarding an optimal, meaning reliable and fast,
approach for the occurring operation case. In order to determine a
suitable test current on the basis of this approach, the computer
program 20 uses statically configured electric system parameters 24
and/or dynamically determined electric system parameters 26 of the
IT power supply system 4.
* * * * *